Since his inauguration two months ago, President Trump has made no secret of his desire to scrap Obama-era climate change policies. From Trump’s pledge to de-fund the Environmental Protection Agency to rescinding the Clean Power Plan, his activities and rhetoric have both taken a troubling direction—but scientists and foreign policy experts alike have held their breath on the biggest development: whether or not Trump would actually follow through on his threat to withdraw the United States from the Paris Agreement, the 2015 accord to slash carbon emissions worldwide in order to save the planet from catastrophic global warming.

The Trump team is facing off behind the scenes, with powerful advisor Steve Bannon urging the President to double down on climate denial, and on the other side, daughter Ivanka Trump and Secretary of State Rex Tillerson warning that American leadership can only be harmed by pulling out of the landmark global accord. News reports indicate that the White House is nearing a decision on which path to take.

Now, with the future of the planet in the balance, nearly fifty-two thousand IFAW members have asked the Trump Administration to put America’s climate policies back on safe ground. In an appeal to the White House, we ask the President to invest in the future by prioritizing clean energy, rebuilding ecosystems to protect wildlife and people alike from drought, wildfires, and other effects of climate change, and working with other countries to fix the problem at the source. You can read the full letter here.

Let us be clear: Reneging on the Paris Agreement would be among the worst environmental decisions in modern history. It’s not just what that would mean for Americans—we desperately need to protect our clean air, water, and natural habitats here in the United States—but also the domino effect that it might launch around the world. Our country has pumped more greenhouse gases into the atmosphere than any other, and the rest of the big polluters (China, India, the EU) may well decide that a deal without U.S. cooperation is no deal at all.

Out of the thousands of decisions a president makes during his term, legacies are built on only a few. How President Trump deals with Paris is one of these choices. It does not get more consequential than this.

IFAW is working around the world to safeguard animals, a task made even more difficult by climate change. Among the many threats animals face, extreme weather events are growing in frequency and intensity, including the Mongolian dzud —when a harsh winter follows summer drought conditions, killing millions of grazing animals and imperiling traditional herders’ way of life.